I’d like to design a motherboard+expansion card project. Is there a way I can create the motherboard and each type of card as separate projects and then export them as parts to use in an assembly? My terminology is coming from solidworks if that helps. That way I wouldn’t have to create dummy parts for connection points and I could visualize the full assembly in 3D without having to export each part and build it up again in MCAD.
Yes. One Project, One PCB is the normal method for working in KiCad at the moment. There are some experiments with KiCad for multiple PCB’s in a sinle project, but that is hackish, and there is no official support.
KiCad works quite nicely with FreeCAD and the “KiCad Step Up Workbench”. KiCad also has: PCB Editor / File / Export / STEP for direct 3D output of the PCB, and with PCB Editor / File / Plot you can also export 2d DXF of the PCB.